Antonyms for the phrase "am on tenterhooks" would include being calm, relaxed, or at ease. The phrase itself means to be anxious, nervous, or on edge, so its opposites would indicate a sense of composure and peace of mind. One could describe feeling confident, carefree, or content, as well as being in a state of tranquility or serenity. Antonyms like nonchalant or unconcerned would indicate a lack of worry or stress, as opposed to the tense and anticipatory feelings implied by the phrase "am on tenterhooks". By using contrasting language, one can highlight the stark difference between these emotional states.